Bender tuned array



, July 8, 1958 A.PETERMANN ETAL 2,842,685

BENDER TUNED ARRAY Filed Dec. 2:5, 1955 Q 2 Sheets-Sheet 1 INVEN TORS NH. PETERMHNN ENCE. C. OAKLEY @XLW ATT RNEY LUCIE WI? L9 35 BY y/ 1958 A.PETERMANN ETAL 2,842,685

BENDER TUNED ARRAY 2 Sheets-Sheet 2 Filed D60. 25, 1955 INVENTORS LUCIENQ PETERMANN' LAWRENCE C. OAKLEY BY ,9

ATTORNEY United States Patent 2,842,685 BENDER TUNED ARRAY Lucien A.Petermann Deans and Lawrence C.' 0 akley, V

Greenbrook Township; N. 1., 'assignorsto Gnlton Industries, Inc., acorporation- 0f New Jersey SClaimsj. Sim-8.3

I I g Our invention relates to bender tuned arrays and in particular tothose bender tuned arrays which employ a plurality of individualpiezoelectric bender elements and which possess a low resonantfrequency. Up to now, it, has been necessary to'increase the dimenslonsof the active element of an electromechanical V transducing system whena lower-frequency was desired. I V

At the lower resonant frequencies; these elements be 'come too large tobe easily produced in commercial quantities withthe consequent resultthat there has been a' limited use of low frequency sonidequipmentp Thishas been particularly apparent in the field of subaqueous detection,ranging and signalling. I

Accordingly, it is a principal object of our invention to provide abender tuned array with a low fundamental resonant frequency.

I It is a further object of our invention to provide a,

- Application December N9. f55,(l09

bender tuned array of reasonable dimensions which may be produced simplyand economically. Other objects andsadvantages of ourv invention will beapparent during thecourse of the following description; 7

" Figure 3 isa perspective view of a further embodiment of ourinvention,

p Figure 4 is a cross-sectional view along theline of v fFigure' 5 is asimplified 'elevational view of avariation rtofflth e embodiment ofFigure'3 wherein the individual 7 bender elements are joined to thediaphragm articulatively} Figure 6 is a simplified elevationaltview of afurther 7,

V variationof the embodimentof Figure 3 wherein -the in- I; dividualbender. elements arejoined to the outer 'member articulatively, and V 7V I, Figure 7 is a simplified elevational view of a still furl to boththe diaphragm and the outer member.

In the drawings, wherein for the purpose of illustration,. 1

thfer variation, of the embodiment of Figure 3 jwherein, the individualbender elements are articulatively joined;

are shown preferred embodiments of our invention, the,

numeral 20 designates the outer ring member, to which is fixedly heldoneend of each bender element 21, the

other end of each bender element 21 is fixedly held to diaphragm 22.Bender element 21 comprises outer elecquencies of the order of 400cycles with the followingfl 7 dimensions:

trodes '23, piezoelectric elements 24, central conductor 25- :andelectrical connection leads 26. Bender elements 28 aretclamped to outerring 27 and to diaphragm 29. Elecis the matching to media ice 38 servesto join 28to'27. r, t e H g Bender tuned arrays of our invention may beemployed as subaqueous. sonic or ultrasonic transmitters or receivers orfor any other ;use which requires low frequency sonic or ultrasonicenergies of high intensities Diaphragm 22 is composed of two discs' of'glass or"- One end of each other suitable insulating material, bender 21is cemented or otherwise fixedly held between the two glass discs of 22with resin or a similar suitable material. Outer ring 20 isformedofalhard resin base piezoelectric elements 24, which may be madeof polarizable ceramic such as barium titanate or other piezoelec tricmaterial, electrodes w23 applied to the outer's'ui faces V of 24and a,central conducting element 25 whichmakes electrical connection to bothinner surfaces of elements'24. Leads 26. from the several individualbenders 21may be connected in many diiferent ways to the driving .genseries-parallel, phases} re- 7 erator such; as series, parallel, versedand so forth.

Byway of example and not by way of limitingthe scope of our invention,we have obtained resonance frequencies as low as 1.6'kc. in liquids and,1.74 kc. in air whenutie lizing bender tuned arrays of the embodimentillustrated in Figures 1 and 2 and with the followingdimensionsiThickness of 22=0.36tmm.; diameter of 22:18 mm);

outside diameter of 20:88 m; inside diameter of 20:

58 mm.; thickness of 20:13 mm.; length. of 2ll'in i width of 21:.066in.; and thickness of 21=.026 in;

Outer ring 27 is a split ring of two metal elements which are heldtogether by screws or similar means. The ends 1 of piezoelectricelements 28 are fixedly held between the 7 metal elements of ring 27.Insulator 35 insulates upper electrode 32 and electrical lead 31 fromouter'ring 27.'

Lower electrode 32 makes electrical contact with ring 27, therebypermitting utilization oflcommon connection '30 for one side ofall-piezoelectric elements 28. fInsula-i tor 36 insulates1owe'r'electrode32 from diaphragm 29 and serves to prevent shortcircuiting 28, 36 further serves to prevent short :circuiting between'27 and-29. -28 is comprised of outer; electrodes .32, piezoelectricelements 33, central conductor 34 and electrical'lead :31; Thepiezoelectric elements 33 may be polan'za-ble ceramic such as bariumtitanate or any other natural or artificial piezoelectric. g Diaphragm29 serves to help determine the resonant V frequencyjof the system sinceit, serves to mass-load the [j elements ZSrfSuitable selection of thearea of 2 9 is important due tothe fact thatr29rs'ervesto match ,the'trans-.5 ducer to the medium. The larger 29 is in area, the-better oflow acoustical impeda q f such as gases and liquids ing the scope of ourinvention, we have first resonant fre Outer diameter of 27:340 mmf;inner diameter of 27:280 .mm.; thickness of 27:20 mm.; 8 elements 28,length=l20 mm. (10 mm. at each end, clamped), thick I nes s=6 mm.,Width=l5 mm., all equally spaced; diameter 29 (metal)= mm; and thickness29:4 mm.

Figure 5 is a simplified drawing of the mounting of, elements 28 (not incompleteydetail) illustrating an articulated connection 37 between-28and 29. 'Maint'ainingtall dimensions as given in the second example'andadding I Fatented July 8,

g 2' across, bender 28 at diaphragm 2,9. Articulated. connee-I I tion 37serves to join 28 to 29 and articulatedlconnection" articulatedconnections 37 between 28 and 29 changes the first resonant frequency to252 cycles.

Figure 6 is a simplified drawing of the mounting of elements 28 (not incomplete detail) illustrating an articulated connection 38 between 27and 28. Maintaining all the dimensions as given in the second exampleand adding articulated connections 38 between 28 and'29 changes thefirst resonant frequency to 215 cycles.

Figure 7 is a simplified drawing of the mounting of elements 28 (not incomplete detail) illustrating articulated connection 37 between 28 and29 and articulated connection 38 between 27 and 28. Maintaining all thedimensions as given in the second example and adding articulatedconnections 37 between 28 and 29 and articulated connections 38 between27 and 28 changes the first resonant frequency to 1357 cycles.

Our invention is not limited to closed circularly shaped outer elementsas illustrated in the figures and described in the specification;polygons, triangles, squares, rectangles, linear arrays and unclosedportions of such geometrical figures may be used as outer elements ofarrays produced in accordance with our invention.

While We have described our invention by means of specific examples andin specific embodiments, we do not wish to be limited thereto, forobvious modifications will occur to those skilled in the art withoutdeparting from the spirit of the invention or the scope of the subjoinedclaims.

Having thus described our invention, we claim:

1. A bender tuned array comprising a plurality of piezoelectric benderelements, one end of each of said piezoelectric bender elements beingfixedly held to a substantially centrally placed, nonflexible diaphragmof substantial mass, the other end of each of said piezoelectric benderelements being fixedly held to an outer element, and electricalconnection means for making connection to the bender elements.

2. A bender tuned array as described in claim 1, wherein one electricalconnection to the said piezoelectric bender elements is common to allthe said piezoelectric bender elements.

3. A bender tuned array as described in claim 1 wherein the saidpiezoelectric bender elements are held to said diaphragm by articulatedjoints.

4. A bender tuned array as described in claim 1 wherein the saidpiezoelectric bender elements are held to said closed outer element byarticulated joints.

5. A bender tuned array as described in claim 1 wherein the saidpiezoelectric bender elements are held to said outer element and to saiddiaphragm by articulated joints.

References Cited in the file of this patent UNITED STATES PATENTS1,693,806 Cady Dec. 4, 1928 2,451,966 Massa Oct. 19, 1948 2,497,680Massa Feb. 14, 1950 FOREIGN PATENTS 235,664 Switzerland Apr. 16, 1945

